Cryogenic refrigerator



April 25, 1967 R. L. BERRY ETAL CRYOGENIC REFRIGERATOR 4 Smeets-sheet 1 Filed April 13, 1965 R. l.. BERRY ETAL 3,315,490

CRYOGENIC REFRIGERATOR April 25, 1967 4 Sheets-Sheet 2 Filed April 13, 1965 R. L. BERRY ETAL CRYOGENIC REFRIGERATOR Aprii 25, wm

Filed April 13, 1955 /nhw R. 1 BERRY ETAL 3,315,490

CRYOGENIC REFRIGERATOR 4 Sheets-Sheet 4 Z, m i m Mm i ,f

Apria 25, 1967 Filed April A13, 1965 United States Patent O ware Filed Apr. 13, 1965, Ser. No. 447,684 16 Claims. (Cl. 62-333) This invention relates to an improved Solvay engine and cryogenic refrigerator t-hat can produce cryogenic temperatures down to about 2.6 K. to 4 K. with relatively high refrigeration powers.

One of the diiiiculties encountered in ultra-low -temperature refrigeration is that the available refrigeration of a cryogen decreases significantly as the temperature of a cryogen decreases toward absolute zero. Heretofore, practical sized cryogenic refrigerators have been developed in which ultra-low temperatures have been obtained with an available refrigeration of less than one watt.

Accordingly, it is an object of this invention to provide a relatively sm'all cryogenic refrigerator that achieves a significant refrigeration power increase at ultra-low cryogenic temperatures.

Another object of this invention is to provide a cryogenic refrigerator of the above type that can operate continuously over long periods of time.

Still another object of this invention is to provide a cryogenic refrigerator that substantially overcomes some of the problems of refrigeration losses that are inherent in :flowing gases.

Yet another object of this invention is to provide a cryogenic refrigerator that is capable of simultaneously providing cryogenic refrigeration at separate temperatures.

The above and other objectives of this invention can be achieved by providing: a Solvay engine; a Joule- Thomson liquefer; and a heat exchanger that operates in the following manner.

The Solvay engine has three pistons each operating 120 out of phase with one another. The pistons cyclically expand a compressed cryogen gas such as helium, thereby decreasing the cryogen temperature to separate low levels at separate portions of the Solvay engine. The refrigeration from the Sovay engine is used to cool compressed cryogen that is -continuously fed to the Joule- Thomson liquefier.

The Joule-Thomson liquefler continuously receives compressed cryogen that iirst ows through a heat exchanger that is in thermal communication with the cold portions of the Solvay engine. Heat from the iiowing cryogen is transferred to cold portions of the Solvay engine to decrease the cryogens temperature. Thus, by the time the cryogen reaches the Joule-Thomson liqueer, it is at a low temperature, whereupon, the liquefier further expands the cryogen to further decrease the cryogens temperature and directs vthe low temperature cryogen against a heat load. The low temperature cryogen is then withdrawn from the heat load in a countercurrent ow over the heat exchanger and is re-fed to a compressor. As 'a result of this continued operation, the temperature of the cryogen in 4the Joule-Thomson liqueer continually decreases until a temperature near the liquefaction temperature of helium is obtained, whereupon the refrigerator stabilizes.

Other objects, features, and advantages of this invention will become apparent upon reading the following detailed description of two embodiments of the invention and referring to the accompanying drawings in which:

FIGS. 1a and 1b are side elevational views, taken partly in cross-section, of a cryogenic refrigerator illustrating the details of a Solvay circuit and a Joule-Thomson circuit;

FIG. 2 is a schematic perspective view illustrating the physical relationship of the different cylinders of the Solvay engine of FIGS. la and 1b;

FIG. 3 is a schematic developed view illustrating the operating principle of the cylinder and piston arrays relative to one another and the refrigerator of FIG. 2;

FIG. 4 is a cross-sectional view taken generally along the line 4 4 of FIG. la and illustrating the intake valveexhaust valve relationship and gas passageway arrangement for the Solvay engine;

FIG. 5 is a developed view of the intake valve cam and the exhaust valve cam surfaces; and

FIG. 6 is a cross-sectional view of a stepped piston embodiment of the Solvay engine cylinder-piston array.

Referring now to the drawings, t-he refrigerator includes a hollow cylindrical housing 13 that encloses a Solvay engine 14 and a Joule-Thomson liqueer 15.

The Solvay engine includes three cylinders 16-18, which 'are mounted within the housing 13 parallel and about the central axis of the housing. Pistons 21-23 are slideably mounted in the cylinders 16-18, respectively, and are adapted for reciprocating motion therein. In operation, the pistons are cycled at out of phase with one 'another by means of a swash plate assembly 24 that is rotated by an electric motor 26 through a gear set 27.

An intake crown cam 2S and an exhaust crown cam 29, located around the periphery of swash plate assembly 24, time and intake valves 31 and exhaust valves 32 associated with each piston and cylinder so that compressed refrigerant gas can be controllably fed from a compressor (not shown) to the Solvay engine 14 and exhausted from t-he Solvay engine. As previously mentioned, each piston and cylinder is timed to operate 120 out of phase with one another over each 360 cycle of operation; thus, the valve pairs also operate 120 out of phase with the other valve pairs.

In operation, refrigerant gas is fed from the compressor through each piston 21;-23, giving up heat to a regenerator 36 mounted therein, thereby resulting in the temperature of the refrigerant decreasing, whereupon the cryogen at the piston head is at the lowest temperature as a result of refrigerant gas expansion cycle.

The refrigeration developed by the Solvay engine 14 is utilized by the Joule-Thomson liqueiier 15 in the following manner. The cold portion of each cylinder stage 16-18 is mounted within a block of heat-conducting material 37 which provides a path for heat conduction between the coils of spirally wrapped heat exchanger 38 and the cylinder.

In operation, a refrigerant gas, such as compressed helium, is fed from a compressor to `that coil of the heat exchanger 38 nearest the base of the Solvay engine 14. The gas flows through the finned spirals or coils of the heat exchanger 38 to the Joule-Thomson liqueer 15. The 'finned heat exchanger coils 41, which are wrapped radially exteriorly of the portion of the piston usually enclosing lthe regenerator 36, can be mounted within blocks of thermally insulating material 40 which aid eciency of the Solvay engine 14.

As previously stated, the cold portions of the Solvay engine stages are mounted within blocks of heat-conducting material 37 which are connected in thermal contact with selected large diameter heat exchanger coils 42 containing a charcoal filter. Heat -from :the refrigerant iiowing in the coil 42 is transferred to lthe Solvay engine |14 causing the temperature of the refrigerant to decrease. After the refrigerant is cooled to a first stage low temperature, it ows from `the coil 42 through heat exchanger cylinder arrangement A ofthe electric motor YVin a re-entrant chamber of Y'cylindrical coils 411 mounted in a subsequent block 40 of lthermally insulating material and thence to other large diameter heat exchanger coils.42 containing a charcoal iilter where ad- Y ditional heat is trans-ferred from the cryogen to a second -17. After three such stages of heat stage coldcylinder transfer operations, the cryogen is fed to the Joule-Thomson liquefier where it -is directed against a heat load 46 such as a parametric amplifier, whereupon, heat is transferred from the parametric amplifier to the expanded lo`w temperature cryogen. Thereafter, the low temperature cryogen is drawn back across the outer surface of the heat exchanger coils 42 in Ya countercurrent ilow to an outlet port near the base of the Solvay engine.

To further aid the eiiiciency of the machine, the colder 13 that contains .the Solvay engine 14 and the'Joule-Thomson liqueiier .-15 is surrounded by an outer cylindrical shell 47 that forms an interspace 48 between the outerV shell 47 and the cylindrical housing portion of the housing 13. This interspace 4S is evacuated .to create a vacuum for thermal insulation.

Referring now to the details of the cryogenic refrigerator, the three stages of cylinders'l, y17, and 18 of Ythe Solvay engineV 14 are mounted to project from one face of a mounting plate 52, -as illustrated in FIG. 2. In opi' eration, as schematically illustrated in the developed view of FIG. 3, the three'cylinders develop progressively colder temperatures with: V`the shortest and largest diameter 16 developing .the Yfirst stage of refrigeration at aV relatively Vhigh temperature; the intermediate length and intermediate diameter cylinder 17 developing a second stage of refrigeration at .the next coldest temperature; and the longest [and smallest diameter cylinder developing a third stage of refrigeration at the coldest temperature in the `Solvay circuit. Generally, as illus- Vtrate'd in FIG. 3, this progressively decreasing tempera- Yture, refrigeration is achieved by means of the heat con- Y ducting disks 37 which Ithermally couple the coldest portion of the first stage cylinder 16 with an intermediate portion of second stage cylinder 17 and third stage cylinder '18, which lthermally couple the coldest portion of the Vsecond stage cylinder 17 with another intermediate portion of the third stage cylinder 18; and which thermally couple the cold portion of all three stages of cylinders 16-18 to a heat exchanger 38 (FIG. la) for the Joule- 'I'homson circuit.

f The pistons are driven within the cylinders 16-18 by the swash'pl-ate assembly -V24 illustrated in LFIG. 1a. In operation, a high speed electric motor 26 transmits rotary motion from a drive shaft to a spur gear set y27. The spur gear set 27 includes `tworparallel axes, external contact gears 53 and '54, and a parallel axes internal contact gear 56. With this gear set, rotationof theswash plate assembly 24, which is fastened to the internal contact spur gear by means of boltsV 5-7, to rotate in the opposite direction of the motor rotation. YAn advantageof this particular arrangement is thatthe inertial forces of the swash plate counteract the inertial forces the .cryogenic refrigerator;

Y YThefswash plate assembly 24'is rotatably mounted witha mounting member 58 on 59 and 61 which provide lowfriction, smooth rotation about the central axis. VThe swash plate assembly 24 includes a cylindrical rim 62 mounted to extend about .the periphery of a plate 63. One face of the plate 63 is inclined atan angle to the axis of rotation and has a bearing aperture formed to extend therein. The aperture rotatably receives a journal of a swash plate 64 which is supported at its periphery on a rollerrbearingV sets roller bearing assembly 66.V

. TheV swash plate -64 drives the pistons Vin a reciprocal sinusoidal motion within the cylinders in the following manner. A swash plate follower 67 is connected to .the lower end of the piston21 and rides on the relatively '.inclined surface of swash plate 64. Thus, as the swash plate Y64 rotates from the position illustrated in PIG. -1a,

the motor V26 causes chamber 68 through:

Y frigeration portion of the s Referring now to the details of the Vfirst stage illustrated n 4 the swash plate follower 67 drives the piston 21 from rightto-left, thereby decreasing the volume in an expansion chamber 68 located between the cylinder head and the piston head. To insure that the piston 2l1 will be sinusoidally driven from left-to-right on an expansion stroke, aV swash plate 69 .is mounted to sandwich a. ilangeV at the base of lthe swash plate follower 67 so that reciprocal motion of the other two cylinders (not shown)Y creates a force moment across the wobble plate 69 which exerts a pulling substantially perfect sinusoidal motion is imparted to the pistons. Y

" To lubricate the swash'plate assembly 24 and swash plate follower mechanism 67, any lubricant is centrifugarlly Y in FIGS. la and 1b, the cylinder 16 is a thinwall,.cylin drical member made of stainless steel or other equivalent material. A cylindrical piston 21 is slideably Yrnounted'for axial movement within the bore of the cylinder 16. To provide low friction movement and to inhibit axial conduction of heat,'the outer shell of the piston 21 is made Y of glass-impregnated epoxy resin. An additionalY advantage of this material is that it has substantially the same coeflicient of expansion as der 16 and, thus,` does not create gas cal binding problems.V The piston Y generator 36; and gas adjacent the piston head; and wall into the expansion Ychamber 68. VThe regenerator 36 can be rnade Vof stacked screens of copper, bronze, or

other materials, which operat'e'by Vreceiving heat romfaV through thejregenerator fromy heat Ytransfer operation takes place,

Vcompressed gas traveling Yright-to-left. VAs this the temperature ofthe regenerator nearest Ythe baseof the piston remains at about ambientV temperature, whereas, the temperature of the regenerator near the piston head remains near the temperature of the gas within 26, thereby dynamically balancingr expansion chamber. Thus, when compressed gas is flowed into the expansion chamber 68, the expansion Y stroke converts theavailable energy of the gas refriger-V ation by decreasing the temperature of the then expanded gas. Subsequently, on the exhaust stroke,

forced back through the regenerator 36, where heat is progressively accepted from Vthe regenerator material,

thereby maintaining'the temperature of the regenerator nearest the piston Vhead at a low temperature'and the temperature nearest the piston base at the'warmer tem- The refrigeration available from the expandV the wall of cylinperature. Y ed gas accepts heat conducted through der 16 by a heat-conducting disk 37, from large diameter coil 42 of the heat exchanger V38 and from intermediate Y portions of the intermediate length cylinder 17 and' the f longest piston 18 (FIG. 2).

Now that the refrigeration cycle of the Solvay circuit Y Y' Vhas been described, the valve operation that controls the Y iiow of compressed cryogen gas to and from'the expanf.Y

force on the swash plate follower 67. An i111-,v portant advantage to this swash plate ytype of drive is thatA travel ofthe swash 'Y On the corn-Y right-to-left, .the check valve 721 built up in the chamber 7-3l the lubricantis forcedfV on the wobble plate 69. The

the stainless steel Ycylinleakage or mechani# 21 is'hollow, therebyfv Y providing a path forcryogen or'gas'ow to the expansionY g an lapertured piston-connecting member'78; an apertured insulator member 79; the re.VV

flow ports81 which extend radiallyY outward fromthe piston interior to the piston side wall Y Y then along the piston side;y

when the piston travels from right-to-left, the'cold expanded gas isv sion chamber 68 to achieve this refrigeration cycle is to be explained.

structurally, each cylinder 16-18 has a separate intake valve 31 and an exhaust valve pair 32. In operation, the compressed gas is selectively fed through the valves to the three cylinders 16-18 so that they operate at 120 out of phase with one another. 'Ihis results in a relatively constant refrigerant intake to the Solvay engine and has the advantage of reducing losses that would otherwise occur during surges and permits smaller gas passageways to be used, thereby eliminating dead space. Still another advantage is that the piston movement is dynamically balanced so that the inertial forces developed hy the reciprocating piston movements substantially cancel one another. The valve action is controlled by means of the intake valve crown cam 28 and the exhaust valve crown cam 29 which are mounted about the periphery of the swash plate assembly rim 62. In general, the crown cams have a shape illustrated by the developed view of FIG. 5, where a related pair of intake valves and exhaust valves operate relative .to one another in accordance with the arbitrarily assigned langular degree marks shown in FIG. and, whereas, the three different valve pairs operate at 120 out of phase with one another.

Since the general operating principles of the intake valves 31 and the exhaust valves 32 are substantially identical, only the operation of the intake valve 31, illustrated in FIG. 1a will be described in detail.

The intake valve 31 is a poppet valve slideably mounted to be axially driven by the crown cam 28. As the crown cam 28 rotates, a cam follower 82 rolls along the cam surface tending to follow the peaks and valleys of the cam surface.

On an intake cycle, the cam peaks drive the cam follower 82 from the right-to-left, thereby driving a valve stern 83 in the same direction through a valve guide 84 to unseat a valve head 86. Compressed gas then flows from an annular passageway 87 past the valve head and into an intake manifold passageway 88 and thence to passageways in the base of the associated piston and through the piston in the manner previously described. After approximately 90 of cam travel, a valve spring 89 biases the cam follower 82 down into a valley portion of the crown cam surface, whereupon an expansion cycle begins. This left-to-right valve motion seats the valve head to seal the gas intake passageway 87 from the intake manifold passageway 88, thereby permitting the gas which has been fed through the associated piston to expand in the expansion chamber and to create refrigeration in the manner previously described.

At the end of the expansion cycle, an associated exhaust valve 32 is opened to permit the expanded gas to be exhausted from the expansion chamber. As previously mentioned, the exhaust valve 32 isrdriven by the crown cam 29 in the same manner that the intake valve 31 is driven by the crown cam 28 and, therefore, the operation of the exhaust valves 32 will not be described in detail.

To aid in describing the gas flow operation, the gas passageways and manifolds are illustrated in dashed line representation in FIG. 4.

The previously referenced -intake gas passageway 87 which is illustrated by dotted lines, extends annually laround the Solvay engine in common communication with the tops of all the intake valves 31 and is supplied with compressed gas through intake tting 90. Immediately below the intake valve heads 86 are the intake manifolds l88 which communicate with the base portion of a related cylinder-piston-regenerator array of the cylinders 16-18.

The exhaust valves, in turn, communicate with the base ends of piston-cylinder and regenerator arrays through exhaust ports 91, whereupon, when the exhaust valve 32 is unseated, the expanded gas from the regenerator is fed past the exhaust valve head and into an exhaust manifold' 92. The exhaust manifolds 92 are, in t-urn, connected in communication with a common annularly-extending exhaust passageway 93 which exhausts to a compressor through conventional exhaust tting 94. An advantage of this particular valving arrangement is that there is little dead space between the valves and the expansion chamber.

Although the above description does not contain a detailed description of the operation of the intermediate length second stage cylinder array 17 and a longer length third stage cylinder 18, it should be understood that the operating principles are much the same. For example, the intermediate length second stage cylinder 17 is of a smaller diameter and includes a longer length regenerator than the cylinder 16, and is in thermal communication with the heat-conducting disk 37 so that the intermediate portion of the cylinder 17 is cooled to about the temperature at the head of the short cylinder 116. Likewise, the intermediate portion of the regenerator associated with cylinder 1S is cooled by a cylinder 16 through the heat-conducting disk 37. This cooling of the regenerator in piston 1S in turn cools the streams of gas passing through-the regenerator in both directions, thereby forcing the gas to be at a temperature closer to that of the regenerator packing in the colder end of the regenerator than in the warmer end. A saving .of refrigeration at the lower temperature expansion is thereby effected. As a result, the temperature at the head of second stage cylinder 17 will be at a colder temperature than the intermediate portion thereof because of the gas expansion and regenerator operation.

The third stage cylinder 18 and piston 23 operate on the same general principles as previously described with reference to cylinders -16 and 17, but does diifer structurally in that a third stage regenerator 1-9 is mounted exteriorly of the piston 23 rather than within the piston and is comprised of lead balls, or the like (FIG. 3). In operation, compressed gas is fed to the expansion chamber 68: through the intake valve 31; through the intake manifold 88; and through the regenerator 19. As the swash plate assembly 24 rotates, the piston 23 reciprocates from left-to-right within the cylinder 18 to expand the compressed gas in the expansion chamber 68, thereby decreasing the gas temperature. As the temperature of the expanded gas decreases, heat conducted along the heat-conducting member 37 is transferred through the thin wall of the cylinder 18 to the cold expanded gas. At the end of the expansion cycle, the piston 23 is driven from right-to-left by the swash plate assembly 24, wherein the expanded cold gas is forced back through the regenerator 19 and exhaust port 91, exhaust valve 3-2 and the exhaust manifold 92.

It should also be noted that the regenerator 19 is in thermal communication with the two other heat-conducting members `37 at two intermediate lengths, wherein the temperature of the regenerator 19 nearest the base of the piston is maintained at about the temperature near the head of the cylinder 15, and the temperature at an intermediate point of the regenerator .19 is maintained at or near the temperature at the head of the cylinder 17. As a result, the temperature at the head of the cylinder 18 and the associated heat-conducting member 37 is maintained at the coldest level.

To retard losses of refrigeration caused by lgas leakage between the side walls of the piston 23 and the cylinder 18, the space between the piston seals 97 and 98 is maintained at about the same pressure as the pressure of the gas within expansion chamber 68. This pressure equalization is achieved by means of a gas port 99 which is connected to communicate the pressure yof the gas within the refrigeration circuit to this space. As a result, there will be substantially no pressure differential across the seal 97, except for any pressure drop that occurs across the regenerator 19, and thus there will be no force that will cause gas leakage =or gas flow past the seal 97. Now that the Solvay engine has been described in detail, the Joule-Thomson refrigeration circuit will be described.

As previously described, the Joule-Thomson circuit Y,tube 103. As previously charcoal yfilter material.

includes a countercurrent heat exchanger 38 which is connected to continuously feed a compressed cryogen to the Joule-Thomson liqueer 15, whereas, the stages of the Solvay engine 14 progressively refrigerate the compressed gas in the heat exchanger 38. Y f

1n operation, compressed ygas is continuously supplied to the -heat exchanger 38 through the inlet lfitting -101 and inlet passageway 102 and to a length of heat exchanger described, the first section of heat exchanger tube is spiralled about the periphery of-a block of thermally insulating material 40. The thermally insulating material 40 can be made of glass-loaded nylon, or the like, and has a smaller diameter than the hollow Y cylindrical housing 13 that surrounds it. As a result,

an interspace is formed between the insulator 40 and the innerrwall of the housing 13. The tubing of the heat exchanger 38 is made 'of beryllium-copper and is formed with fins extending around the exterior surface by a tubefinning apparatus described in U.S. Patent No. 3,163,083, rgranted Dec. 29, 1964, to A. S. Chapman et al. As a l'result of the above combination, a path for a countercurrent gas ow over the surface of the coils 41 of heat exchanger 38 is provided for purposes Vto be described shortly. s e

f -The last Yheat exchanger coil 41 spiralled about the insulating material 40V is connected to feed the com-l pressed gas to aflarge diameter coil 42 containing a The compressed gas enters the charcoal iltercoil 42 at the lower end thereof and is transferred around the coil 42V and out at the lowerV end just before making a full 360 cycle therearound. While. vthe compressed gas is flowing through the charcoal'filter ,coil 42,V it is in intimate thermal conta-ct with theV rst stage heat-conducting disk 37, which is in turn, in thermal VYcontact with the head of the Vfirst stage cylinder 16.A VThe heat exchanger disk 37 isrmade ofanecient Vheatconducting material, such as aluminum or copper, which circuit Yto the -cold expanded gasv ofV the Solvay circuit. As a result of the heat transfer, the compressed |gas `leaving the charcoal filter 42 willhave a lower tempera- '.ture than when it entered.

VYThe lower temperature compressed gas from the first stageV coil 42 Hows through Vanother spiral of heat ex- 'changer coils 41 surroundinga block of insulating material 40 and is coupled through a second refrigerator stage disk lof thermally-conducting material 37 to a seci Vhas the advantage :of readilyV transferring heat from the Y .compressed gas Within coil 42of AtheJoule-Thomson housing 13. A vacuum tap valve 111a can be connected.

to a vacuum pump (not shown) to evacuate the inter-V space 48 formedrbetween the Vouter sleeve 47 .andthe A mounting housing 13. VAfter'thei'nterspace 48hasbeen; evacuated to a high vacuum level, the Vvacuum'tapvalve V. 111a may be closed, whereupon, any gases entrapped therein are cryopumped by thercryogenic refrigerator to v As had happened when the gas i l ldisk 37, the compressed gas gives up additional heat to the second stageV of the Solvay engine through the heatconducting material 37 and, as a result, is refrigerated` to the next lower temperature level. Y The gas fed from this second stage charcoal filter coil Y 42 is spiralled around another block of insulating material 40 by means of heat exchanger coils 41 and through a disk of thermally-'conducting material Y40 to a third stage'- charcoal filter coil'42. The compressed gas flowing in the third charcoal lilterocoil 42 gives up additional heat to the third stage of the Solvay engine through theY disk of the thermally-conducting material in Vthe manner previously described. After the gas has thus gone'rthrough the three stages of cooling, it flows from the third stage charcoal filter coil 42 through another Vset of spiralled heat exchanger coils 41 spiralled about the block of insulating material 40 and thence radially Y same reference characters throughout and, as a result,V

8 inward through a length of tubing 106 to a Joule- Thomson gas liquefler 15.

The Joule-Thomson gas liqueer 15 expands the compressed gas to further reduce its temperature down to` its liquefaction temperature. Thus, where the compressed gas flowing through the heat exchanger 38 is helium,

the resultant temperature developed by the Joule-Thomson liqueier 15 `and heat exchanger 38, stabilizes at around 4 K. The Joule-Thomson liqueer would operate in accordance with the principles discussed in Marks Mechanical Engineers Handbook, 6th ed. pp. 4-67.

A heat load 46, such as aY parmetric amplifier, is

mounted on a heat-conducting mounting plate 107 so that heat from the heatV load is transferred to the expanded low temperature Vgas flowing. from the Joule-Thomson As the expanded gas flows along the inner surface of, the mountingy plate 107, it Vpicks up heat therefrom and is drawn back to the compressor over the finned surfaces ofthe heat exchanger coil 41 and through'the 'interspace formed between Vthe stacked disks ofi-insulating` material 40 Vand thermally-conducting materialV 37, to

chamber109 and through anoutlet port 111 formed through the refrigerator wall. s It should of course be understood that thedisks of thermally insulating material 40 can be eliminated'without seriously affecting theoperation of the cryogenic:VV refrigerator. VIn such cases, a shield or the like Vwould be needed t-o restrict the flow of the countercurrentV gas to an area immediately adjacent the outer housing 13 and heat exchanger 38. VAn `advantage of eliminatingY the insulating disks '40 is that the refrigerator can be cooled downpquicker.

kTo provide thermalV isolationV between the" ambient,V Y atmosphere and the Yrefrigerator circuits, an outer'sleeve 47 is mounted over and about the hollow cylindrical insure an extremely highV vacuum. Additional thermal Visolation between the cold portions of the refrigeratorand the warmer portions by-the thermallyconducting disks 37 which absorb heatfrom axially-conducting heatVV paths such as electrical leads, Vwallrmaterials, and block radiation Yfrom warmer Yportions of the refrigerator unit.

One important featurerof the above-described refrigeration-'is that its operation is not undulyV affected byV changes in its orientation relative toa gravitational vector; Thus, the refrigerator has ,theV advantage of being mountable in any position or orientation.V

One embodiment of'the Solvay engine hasV been described and illustrated as having three separate, pistons of three separate lengths and diameters, each developing refrigeration. i

Since the only significant structural change Vbetween the two embodiments of Solvay engines is in the stepped pistons and stepped cylinders, those portions of therefrigerator that are identical to Vthe portions contained'in the first embodiment of Vthe refrigerator are given lthe will not be redescribed.

The second embodiment of the Solvay engine includes a Y hollow, stepped cylinder 112 which is adapted to slideably receive :a stepped piston 113. The stepped cylinder 112 and stepped piston 113 are adapted to form three variable volume expansion chambers 114, 116, and 117 which develop progressively colder stages of refrigeration. The piston Walls are made of a fiberglass impregnated epoxy resin that has substantially the same cefficient of thermal expansion as the stainless steel cylinder 112.

In operation, compressed gas is selectively fed through the apertured piston-connecting member 78 and through the apertured insulating insert 79 to a first regenerator 118 in the larger diameter portion of the stepped piston 113. The compressed gas enters the first stage regenerator 118 -at about ambient temperature and progressively gives up heat to the regenerator material so that the gas flowing in the re-generator portion nearest the first stage expansion chamber 114 is at about the same temperature as the temperature of the -gas in the first expansion chamber 114. Radially extending gas ports 119 enable gas to iiow to and from the first stage expansion chamber 114 during the reciprocating operation of the piston.

A second stage yof refrigeration is obtained at the second stage expansion chamber 116 by gas owing through an apertu-red insulator insert 121 mounted between the first stage regenerator 118 and a second stage regenerator 122. The temperature of the cryogen gas entering the second stage regenerator 122 is at about the temperature in the first stage expansion chamber 114. As this cryogen gas flows through the second stage regenerator 122, it progressively transfers heat to the regenerator material until it is at about the temperature lof the second stage expansion chamber 116 when nearest the second stage expansion chamber. The cold gas is transferred to and from the second stage regenerator 122 in the second stage expansion chamber 116 by means of the radially extending gas ports 123. lPecause of the progressive cooling, the temperature of gas Within this second stage expansion chamber 116 is lower than the temperature of gas in the first stage expansion chamber 114.

Cryogen gas entering a third stage regenerator 124 of lead balls, ows through an `apertured thermal insulator insert 126 and enters the third stage regenerator at about the temperature of the -gas within the second stage expansion chamber 116. As the cryogen ows through the third stage regenerator 1124, it gives up heat to the regenerator material rand flows into the third stage expansion chamber 1=17 through the gas ports 128 at a temperature near the temperature of the third stage expansion chamber. As a result of the gasexpansion within the third stage expansion chamber 117 and the progressive or successive temperature drops of the gas flowing through the three stages of the engine, the temperature of the third stage expansion chamber 117 is lower than the temperature of the two other stages.

As with the previous embodiment of the Solvay engine, the refrigerator stages cool the compressed cryogen owing through the heat exchanger coils 41 and 42.

One refrigerator that has been constructed, weighed about 50 lbs. and had an over-all dimension of about 6 inches in diameter and about 26 inches in length. When operated, the Solvay circuit temperature at the first stage was at about 150 K., the temperature at the second stage Was at about 5 0 K. and the temperature at the third stage was at about 15 K. The Joule-Thomson circuit obtained refrigeration at about 4.5 K. and about 2 watts of refrigeration.

While the salient features of the invention have been shown and described with respect to particular embodiments, it will be readily apparent that numerous modifications may be made within the spirit and scope of the iuvention and it is, therefore, not desired to limit the invention to the exact details shown except insofar as they may 4be defined in the following claims.

What is claimed is:

1. A device for cooling a heat load comprising: a first refrigeration circuit including a refrigerator having a cylinder and piston means forming a refrigeration stage expansion chamber and Valve means coupled to feed and exhaust compressed Igas to and from said expansion chamber; and a second refrigeration circuit to receive compressed gas and including a heat exchanger means thermally coupled to the refrigerator, and a `loule-Thomson liquetier coupled to receive a flow of compressed gas from said heat exchanger means, said heat exchanger means transferring heat from the compressed gas contained therein to said refrigerator stage to cool the compressed gas owing to the Joule-Thomson liquefier whereby the Joule- Thomson liqueer expands and further cools the received gas, and means to transfer heat from the load to the expanded and cooled gas of the Joule-Thomson liquelier, said heat exchange means including line means carrying the expanded and cooled gas from the liqueer into thermal heat exchange relationship with the heat exchanger received compressed gas.

2. A device for cooling a heat load comprising: a first refrigeration circuit including a Solvay engine refrigerator having a cold refrigeration stage; and a second refrigeration circuit to receive compressed gas and including a heat exchanger means thermally coupled to the refrigerator, a Joule-Thomson liqueer coupled to receive a flow of compressed gas from said heat exchanger, said heat exchanger means transferring heat from the compressed gas contained therein to said refrigerator stage to cool the compressed gas flowing to the Joule-Thomson liqueiier whereby the Joule-Thomson liqueier expands and further cools the received gas, and means to transfer heat from the load tothe expanded and cooled gas of the liqueer, said heat exchange means being adapted to receive the expanded and cooled gas from the liqueer and bring the latter into thermal heat exchange relationship with the heat exchanger received compressed gas.

3. A device for cooling a heat load comprising: a first refrigeration circuit including a refrigerator having a plurality of cylinders and piston arrays each forming a refrigeration stage expansion chamber of progressively colder temperature; and -a second refrigeration circuit including a heat exchanger means thermally coupled to the refrigerator and adapted to continuously receive compressed gas, a Joule-Thomson liquetier coupled to continuously receive compressed gas from said heat exchanger means, said heat exchanger means transferring heat from the compressed gas contained therein to said progressively colder refrigerator stages to progressively cool the compressed gas flowing to the Joule-Thomson liquefier whereby the Joule-Thomson liqueer expands and further cools the received gas, and means to transfer heat from the load to the expanded and cooled gas of the lique'er, and other means establishing thermal communication between the arrays whereby the refrigerating effect of one of the cylinder and piston arrays is transferred to at least one of the other cylinder and piston arrays.

4. A device for cooling a heat load comprising: a first refrigerator circuit including a Solvay engine refrigerator having a plurality of progressively colder refrigeration stages; and a second refrigeration circuit including a heat exchanger means thermally coupled to the refrigerator and receiving compressed gas, and a Joule-Thomson liqueier coupled to continuously receive compressed gas from said heat exchanger, said heat exchanger transferring heat from the compressed gas contained therein to said progressively colder refrigerator stages to progressively cool the compressed Vgas flowing to the Joule-Thomson liquefier whereby the Joule-Thomson liquefier expands and further cools the gas, means to transfer heat from the load to the expanded and cooled gas of the liquefier, said heat exchange means including line means carrying the expanded and cooled gas from the liquefier into thermal heat exchange relationship with the heat exchanger received compressed gas, and thermal transfer means interconnecting the progressively colder refrigerating stages whereby the refrigerating effect of at least one of said stages is transferred to at least another of said stages.

5. A device for cooling a heat load comprising: a first refrigeration circuit including a refrigerator having a plurality of cylinder an-d piston arrays, each forming a refrigeration stage expansion chamber, one of said expansion chambers creating refrigeration at a tempearture warmer than the other two expansion chambers and another said expansion chamber creating refrigeration at a cooler ternperature thau'the other two expansion chambers; and a second refrigeration circuit including a heat exchanger means thermally coupled to the refrigerator and receiving compressed gas, and a Joule-Thomson liqueer coupled to continuously receive compressed gas from said heat-'exchanger means, said heat exchanger means transferring heat from the compressed gas contained therein to said progressively colder expansion chambers to progressively cool the Vcompressed lgas flowing to theYIoule-Thomson liqueer, whereby the Joule-Thomson liqueer expands and further cools the received gas, means Vto transfer heat from the load to the expanded and cooled gas of the liqueer, and thermal transfer means connecting certain of said arrays and operative to transfer the refrigerating eiect of at least one ofV said chambers to at least one of said other arrays. Y

6. A device for cooling a heat load comprising: a first refrigeration circuit including a Solvay refrigerator having a plurality of cylinder and piston arrays, each forming a refrigeration stage expansion chamber, one of said expansion chambers creating refrigeration at a temperature warmerrthan the other two expansion chambers and another said expansion chamber creating refrigeration at a cooler temperature than Vthe other two expansion cham- Vjbers; and a second refrigeration circuit thermally coupled to the refrigerator and including'a Yheat exchanger means adapted to continuously receive compressed gas,*and a Joule-Thomson liqueiier coupled to continuouslyY receive compressed gas from said heat exchanger means, ,said

'heat exchanger means transferring heat from the compressedV gas contained therein to said progressively colder expansion chambers to progressively cool the compressed Y gas flowing to the Joule-Thomson-liqueer, whereby the Joule-Thomson liqueer expands and further -cools the received gas, means to transfer heat from the load to the expanded and cooled change means including line means-carrying and cooled gas from the liqueer into thermal heat eX- f change relationship with the heat exchanger received com-Y pressed gas,

and thermal interlockingY means physically joining the arrays and operative to transfer the refrigerating effect of certain of saidtchambers to the otherr of said Varrays.' i

V 7. A device for cooling a heat Vload comprising: a `first refrigeration circuit Yincluding a refrigerator having a plurality of VYcylinder and piston arrays, each forming aV refrigeration stage expansion chamber, one of said expan- Y sion chambers creating Vrefrigeration at a temperature Y warmer Vthan the other two expansion chambers and another Vsaid expansion chamber creating refrigeration at a cooler temperature than the other two expansion cham- Vbers,rsaid one chamber being thermally coupled to cool Van intermediate portion of the other two said pistoncylinder arrays and the other said expansion chamber creating refrigeration at a temperature between the cooler and Warmer temperature refrigeration and being coupled to'cool an intermediate portion of the cooler cylinderpiston array to the intermediate temperature, a'second refrigeration circuit including a heat exchanger means thermally coupled to the refrigerator and adapted to continuously receiveV compressed gas, and a Joule-Thomson liquefier coupled to continuously receive compressed gas from said heat exchanger means, said heat exchanger means transferring heat from the compressed gas contained therein to said progressively colder expansion chambers to progressively cool the compressed gas owing to the Joule-Thomson liquefier, whereby the Joule-Thomson liqueiier expands and furtherV cools the received gas,

and means to transfer heat from the road to the expanded and cooled gas of the Joule-Thomson liqueer.

8. A device for cooling a heat load comprisig: first refrigeration circuit including a Solvay refrigerator having Y having a plurality of cylinder and piston arrays, Yeach forming a refrigeration stage expansion chamber, one of said expansion chambers creating refrigeration at a temperature warmer than the other two expansion chambers and another said expansion chamber creating refrigeration at a cooler temperature than the other ltwo expansion chambers, said one chamber being thermally coupled to cool an intermediate portion of the other two said pistoncylinder arrays to the warmer temperature and the other s said expansion chamber creating refrigeration at a tem-v continuously receiveV compressed gas from-said heat eX'- changer means, said heat exchanger means transferring heat from the compressed gas contained therein to said progressively colder expansion chambers to progressively cool the compressed gas owing to the Joule-Thomson liqueer, whereby the Joules-Thomson liqueer expands and further cools the received gas, and means to transfer heat from the load to the expanded and cooled gas of the Joule-Thomson liquefier.

9. A device for cooling a heat load comprising: a first refrigeration circuit including a refrigerator having a plu- Y arrays, each 'forming a re- Y rality of cylinder and Vpiston Y frigeration stage expansion chamber, one of sa1d `expansion chambers creating refrigeration at aV temperature thermally coupledV to Vthe -warmer than the other two Vexpansion chambersl and gas of the liqueer, saidheat ex- Y the Vexpanded and a Joule-Thomson Y ing refrigeration at a Vtemperature Y warmer ,temperatureV refrigeration and belng coupled by another said expansion chamber creating refrigeration at a cooler temperature than the other two expansion chambers, saidY one chamber being thermally coupled by a thermally conducting disk to cool an Vintermediate portion ofthe other Ytwo said piston-cylinder arrays to the warmerl temperature and the other said expansion chamber creatbetween the cooler and t Y Y i a thermally conducting disk to coolY an intermediate por'- tion of the cooler cylinder-piston array to the intermediate temperature; a second refrigeration circuit including a heat exchanger meanslthermrally coupled to the refrigerator and adapted to continuously receive compressed gas, liquefier coupled to continuously receive compressed gas from saidrheat exchanger means, said heat exchanger means Ytransferring heat-from: the compressedv gas contained therein to said progressively colder expansionV chambers whereby the Joule-Thomson liqueer expands and further cools the received gas, and means to transferheatfrom the load to the expanded and cooled Thomson liqueer. f

10. A device for cooling arheat load comprising: a first another said expansion chamber creating refrigeration `at f a coolerrtemperature than the other two expansion cham/-` bers, said one chamber being thermally coupled by .a thermally conducting disk to cool an intermediate portion to progressively cool thercom-v. 'Y pressed gas flowing to the YJoule-Thornson hq'uefier,"

gas of Ythe Jouleeach `forming a reof the other two said piston-cylinder arrays to the warmerV temperature refrigeration andthe other said expansion chamber creating refrigeration'at a temperature between Y j?VVV the cooler and warmer temperatures-refrigeration and Y Y disk to cool an Y being coupled byatthermally conducting intermediate portion of the cooler cylinder-piston array to the intermediate temperature; a second refrigeration circuit including a heat exchanger means thermally coupled to the refrigerator and mounted about said rst stage refrigeration circuit and adapted to continuously receive compressed gas, and .a Joule-Thomson liquefier coupled to continuously receive compressed gas from said heat exchanger means, said heat exchanger means transferring heat from the compressed gas contained therein to said progressively colder expansion chambers to progressively cool the compressed gas owing to the Joule-Thomson liqueiier, whereby the Joule-Thomson liqueiier expands and further cools the received gas, and means to transfer heat from the load to the expanded and cooled gas of the Joule-Thomson liquefier.

11. A Solvay engine comprising: a plurality of cylinders and piston means, each operable to form variable volume expansion chambers, said cylinder-piston means being arranged about a central reference axis at equal angular displacement from one another; a plurality of regenerator means each individually coupled to an individual one of the expansion chambers for communicating gas thereto and therefrom; a plurality of valve means each individually coupled to feed compressed -gas to and exhaust expanded gas from an individual expansion chamber through said individual regenerators; and swash plate means coupled to drive said pistons relative to said cylinders for varying the volume of the expansion chambers in a sinusoidal motion, said swash plate further operating each of said plurality of cylinder-piston means at equally out of phase differences from the operating phase of one another.

12. A Solvay engine comprising: a plurality of cylinder and piston means, each operable to form variable volume expansion chambers, said cylinder-piston means being symmetrically arranged about a central reference axis at equal angular displacements; a plurality of regenerator means each individually coupled to an individual one of the expansion chambers for communicating gas thereto and therefrom; a plurality of valve means each individually coupled to feed compressed gas to and exhaust expanded gas from the individual expansion chambers through said regenerators; swash plate means coupled to drive said pistons relative to said cylinders for varying the volume of the expansion chambers in accordance with a sinusoidal motion, said swash plate further driving said plurality of cylinder-piston arrays at equal spaced phase differences from the operating phase of one another; and crown cam means coupled to said swash plate for opening and closing said valve means in time with said swash plate cyclic operation.

13. A Solvay engine comprising: a plurality of stepped cylinder and stepped piston means, each operable to form Variable volume expansion chambers, said cylinder-piston means being symmetricallyarranged about a rotation axis; a pluralityrof vregenerator means each individually coupled to an individual one of the expansion chambers for communicating gas thereto and therefrom; a plurality of valve means each individually coupled to feed compressed gas to and exhaust expanded gas from the individual expansion chambers through said regenerators; swash plate means cou-pled to drive said pistons -relative to said cylinders for varying the volume of the expansion chambers in accordance with a sinusoidal motion, said swash plate further driving said plurality of cylinderpiston arrays at equal spaced phase differences from the operating phase of one another; and crown cam means coupled about the peripheral portion of said swash plate for opening and closing said valve means in time with said swash plate cyclic operation.

v14. In a refrigerator of the type having a cylinder and a piston movably mounted in the cylinder to form a variable volume expansion chamber, an improvement therewith comprising: a iirst pist-on seal and a second piston seal mounted about the periphery of the piston in two spaced apart axially displaced planes to form an interspace between the cylinder wall and the piston wall at the end of the piston remote from the expansion chamber; a regenerator coupled at one end to communicate a refrigerant gas to and from the expansion chamber, and coupled at the other end of a controlled source of refrigerant gas; and means coupled to communicate to the interspace between the pist-on seals the pressure created by the controlled source of refrigerant gas and by the piston-cylinder operation for equalizing the pressure at the interspace between the seals with the pressure of the gas in the expansion chamber whereby refrigerant lgas leakage along the piston and cylinder wall interface is eliminated.

1S. In a refrigerator of the type having a cylinder and a piston movably mounted for a reciprocal motion Within the cylinder to operably form a variable volume expansion chamber between the cylinder head andthe piston head, an improvement therewith comprising: a first piston seal and a second piston seal mounted between the piston Wall and the cylinder wall at two spaced apart axially displaced planes to form an interspace between the cylinder Wall and the piston Wall at the end of the piston remote from the expansion chamber; a regenerator coupled at one end to communicate a refrigerant gas to and from the expansion chamber, and coupled at the other end to a source of refrigerant gas; means coupled to communicate the pressure of the gas within the expansion chamber and the pressure drop developed across the regenerator to the interspace between said piston seals for equalizing the pressure at the seals with the pressure of gas within the expansion chamber whereby refrigerant gas leakage along the piston wall and cylinder wall interface is eliminated. 16. In a refrigerating engine, a plurality of cylinders having movable pistons therein,

each cylinder and piston deiining a variable volume expansion chamber, regenerator means communicating with each chamber to accommodate the entrance and exit of a refrigerating gas into the regenerating means and to said chamber, valve means communicating with a source of refrigerating gas and the regenerating means to allow the emission and exit of said gas to the respective regenerator means and the associated chamber, and means establishing thermal communication between at least one of said chambers and the gas entering another chamber to cool said last-mentioned gas prior to entry into the related chamber.

References Cited by the Examiner UNITED STATES PATENTS 3,091,092 5/1963 Dros 60-24 X 3,115,015 12/ 1963 Hogan 62-6 3,125,863 3/1964 Hood 62-175 3,128,605 4/ 1964 Malaker et al 62-6 3,183,662 5/ 1965 Korsgren 62-6 X 3,221,509 12/ 1965 Garwin 62-6 ROBERT A. OLEARY, Primary Examiner. W. E. WAYNER, Assistant Examiner. 

1. A DEVICE FOR COOLING A HEAT LOAD COMPRISING: A FIRST REFRIGERATION CIRCUIT INCLUDING A REFRIGERATOR HAVING A CYLIN DER AND PISTON MEANS FORMING A REFRIGERATION STAGE EXPANSION CHAMBER AND VALVE MEANS COUPLED TO FEED AND EXHAUST COMPRESSED GAS TO AND FROM SAID EXPANSION CHAMBER; AND A SECOND REFRIGERATION CIRCUIT TO RECEIVE COMPRESSED GAS AND INCLUDING A HEAT EXCHANGER MEANS THERMALLY COUPLED TO THE REFRIGERATOR, AND A JOULE-THOMSON LIQUEFIER COUPLED TO RECEIVE A FLOW OF COMPRESSED GAS FROM SAID HEAT EXCHANGER MEANS, SAID HEAT EXCHANGER MEANS TRANSFERRING HEAT FROM THE COMPRESSED GAS CONTAINED THEREIN TO SAID REFRIGERATOR STAGE TO COOL THE COMPRESSED GAS FLOWING TO THE JOULE-THOMSON LIQUEFIER WHEREBY THE JOULETHOMSON LIQUEFIER EXPANDS AND FURTHER COOLS THE RECEIVED 